Aromatic polycarbonate polymers have found wide use as engineering thermoplastics, having inherent toughness and clarity. In particular, polycarbonate blends using polyorganosiloxane-polycarbonate block copolymers are widely used. These copolymers possess enhanced properties such as low temperature impact strength, low temperature ductility, improved processability, and fire retardance. The polyorganosiloxane-polycarbonate block copolymers can be advantageously blended with various proportions of aromatic polycarbonate polymers to prepare thermoplastic molding compositions capable of meeting the wide range of requirements for high and low temperature properties. By varying the selection of the polycarbonate polymer and the proportions of blend ingredients, a wide range of properties may be obtained, starting with a single polyorganosiloxane-polycarbonate block copolymer. Furthermore, the mechanical properties of these blends can be greatly improved by reinforcement with glass fibers making them useful for applications that have stringent performance requirements.
Today, the consumer electronics industry is increasingly calling for ultrastiff tough (UST) materials that have specific mechanical and structural properties to replace metal. These materials must be capable of being injection molded into thin wall parts (i.e., 10 inch tablet cover that is 1.0 mm thick) that are extremely dimensionally stable with little to no warpage and have a high aspect ratio. Good weldline strength and a flat weldline without bumps are also needed to ensure the mechanical integrity of thin-walled parts with a multi-gate design. The materials must also fulfill flame retardant requirements, typically V0-V1 ratings at <=1.0 mm. Glass-reinforced polycarbonate blends generally provide superior mechanical properties in comparison with traditionally used thermoplastic molding compositions such as nylon-based blends, and therefore, may be the best candidate to meet the criteria set forth for UST materials in consumer electronic applications.
There is an unmet need, however, for developing Mass-reinforced polycarbonate blends using polyorganosiloxane-polycarbonate block copolymers, which have the optimal balance of toughness and strength while also retaining other properties, such as low temperature ductility, good processability and fire retardance. Until now, the selection and the proportions of the polycarbonate polymer, the polyorganosiloxane-polycarbonate block copolymer, and the glass fiber needed to achieve the best mechanical performance of these polysiloxane-polycarbonate block copolymers blends has been unknown.
Accordingly, the present disclosure provides thermoplastic compositions that are glass-fiber reinforced blends of polyorganosiloxane-polycarbonate block copolymer and polycarbonate polymer that possess superior mechanical properties.